ORAU Team

NIOSH Dose Reconstruction Project

Technical Basis Document for the Y-12 National Security Complex

– Occupational Medical Dose

Document Number:

ORAUT-TKBS-0014-3 

Effective Date: 04/18/2006

Revision No.: 00 PC-3 

Controlled Copy No.:_______

Page 1 of 20

Subject Expert: William E. Murray

Document Owner

Approval: Signature on File Date:12/16/2003

William E. Murray, TBD Team Leader

Approval: Signature on File Date: 12/16/2003 Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Date: 12/16/2003 Richard E. Toohey, Project Director

Approval: Signature on File Date: 12/16/2003 James W. Neton, OCAS Health Science Administrator

Supersedes:

None

TABLE OF CONTENTS

Section

Record of Issue/Revisions ...................................................................................................................

Page

3

Acronyms and Abbreviations ...............................................................................................................5

3.1 Introduction ..............................................................................................................................6

3.2 Examination Frequencies.........................................................................................................7

3.3 Equipment and Techniques......................................................................................................8

3.4 Organ Dose Calculations .........................................................................................................9

3.5 Uncertainty.............................................................................................................................11

References ........................................................................................................................................13

Glossary ............................................................................................................................................14

Attachment 3C Occupational Medical Dose......................................................................................16

3C.1 Y-12 Medical X-ray Program.................................................................................................. 17

3C.2 Organ Doses from Medical X-rays ......................................................................................... 17

3C.3 Dose Reconstructor Instructions ............................................................................................ 17

3C.3.1 Assignment of Organ Doses from X-ray Procedures: Maximizing 

Approach for Dose Reconstructions .............................................................................. 18

3C.3.2 Assignment of Organ Doses from X-ray Procedures: Best Estimate 

Approach for Dose Reconstructions .............................................................................. 18
Effective Date: 12/15/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-3 Page 2 of 20

LIST OF TABLES

Table

3-1 Frequency of occupational chest x-rays at Y-12.......................................................................

Page

7

3-2 Description of the X-ray equipment used at Y-12 ..................................................................... 8

3-3 Technique factors used for each type of X-ray equipment........................................................ 9

3-4 Entrance kerma values for Y-12 chest x rays ........................................................................... 9

3-5 Analogues for Interactive Radio-Epidemiological Program (IREP) organs 

not included in ICRP (1982) ................................................................................................... 10

3C-1 Frequency of occupational chest x-rays at Y-12..................................................................... 17

3C-2 Organ doses (rem) for a beam quality (HVL) of 2.5 mm Al and 80 kVp 

(1943-1947) ...........................................................................................................................19

3C-3 Organ doses (rem) for a beam quality (HVL) of 2.5 mm Al and 80 kVp 

(1948-1968) assuming no collimation..................................................................................... 19

3C-4 Organ doses (rem)a for a beam quality (HVL) of 2.5 mm Al and 80 kVp 

(1969-January 1982).............................................................................................................. 20

3C-5 Organ doses (rem)a for a beam quality (HVL) of 3.5 mm Al and 110 kVp 

(January 1982-present).......................................................................................................... 20
Effective Date: 04/18/2006 Revision No. 00 PC-3 Document No. ORAUT-TKBS-0014-3 Page 3 of 20

RECORD OF ISSUE/REVISIONS

ISSUE 

AUTHORIZATION 

DATE EFFECTIVE DATE REV. NO. DESCRIPTION

12/15/2003 12/15/2003 00 New technical basis document for the Y-12 National 

Security Site – Occupational Medical Dose. First 

approved issue. Initiated by William E. Murray.

12/15/2003 09/09/2004 00 PC-1 Deletes references to Kathren et al., to be published 

on pages 7, 11, 17 and 18,. This document has not 

been published. Adds references on pages 7, 11, 17 

and 18 for ORAU (Oak Ridge Associated 

Universities) 2003, Technical Information Bulletin:

Dose Reconstruction from Occupationally Related 

Diagnostic X-ray Procedures, ORAUT-OTIB-0006 

Rev 00, Oak Ridge, Tennessee. November 14, 2003. 

First approved page change revision. Initiated by 

William E. Murray. Approval:

Signature on File________________ William E. Murray, TBD Team Leader09/08/2004

Signature on File________________ Judson L. Kenoyer, Task 3 Manager08/27/2004

Signature on File________________ Richard E. Toohey, Project Director08/30/2004

Signature on File________________ James W. Neton, Associate Director for Science09/09/2004

12/15/2003 10/11/2005 00 PC-2 Page change initiated to incorporate the definition of 

U.S.C. on page 4 and details for the definition of a 

DOE facility on page 5. No sections were deleted. 

Second approved page change revision. Retraining 

is not required. Initiated by William E. Murray. 

Approval:

William E. Murray, TBD Team Leader

Signature on File_________________10/06/2005 

Judson L. Kenoyer, Task 3 Manager

Signature on File _____________ 10/04/2005 

Richard E. Toohey, Project Director

Signature on File____________ 10/04/2005 

James W. Neton, Associate Director for Science

Signature on File______________ 10/11/2005 
Effective Date: 04/18/2006 Revision No. 00 PC-3 Document No. ORAUT-TKBS-0014-3 Page 4 of 20

12/15/2003 04/18/2006 00 PC-3 Page change initiated to revise text in Table 3-5 on 

page 10 in Section 3.4 to remove reference that 

uterus is a surrogate for ovaries. No changes 

occurred as a result of formal internal review. No 

sections were deleted. Text on page 10 was revised 

in response to NIOSH formal review. Third approved 

page change revision. Retraining is not required. 

Initiated by William E. Murray. Approval:

William E. Murray, TBD Team Leader

Signature on File__________________ 04/17/2006 

John M. Byrne, Task 3 Manager

Judson L. Kenoyer Signature on File for 04/17/2006 

Edward F. Maher, Task 5 Manager

Signature on File __________________ 04/14/2006

Kate Kimpan, Project Director

Signature on File____________ __ 04/18/2006 

James W. Neton, Associate Director for Science

Signature on File______________ __ 04/18/2006 
Effective Date: 10/11/2005 Revision No. 00 PC-2 Document No. ORAUT-TKBS-0014-3 Page 5 of 20

ACRONYMS AND ABBREVIATIONS

Al Aluminum

cGy centigray

DCF Dose conversion factor

DOE Department of Energy

eq. Equivalent

ESE Entrance skin exposure

GE General Electric

Gy gray

HVL Half value layer

ICRP International Commission on Radiological Protection

IREP Interactive Radio-Epidemiological Program

keV kiloelectronvolt

kVp kilovolts peak

mA milliampere

MeV Megaelectronvolt

mGy milligray

mm millimeter

NCRP National Council on Radiation Protection and Measurements

PA Posterior/anterior

PFG Photofluorographic

POC Probability of causation

RMS Root-mean-square

s second

SID Source-to-image distance

SSD Source-to-skin distance

TBD Technical Basis Document

TEC Tennessee Eastman Corporation

U.S.C. United States Code

Y-12 Y-12 National Security Complex
Effective Date: 10/11/2005 Revision No. 00 PC-2 Document No. ORAUT-TKBS-0014-3 Page 6 of 20

3.1 INTRODUCTION

Technical Basis Documents and Site Profile Documents are general working documents that provide 

guidance concerning the preparation of dose reconstructions at particular sites or categories of sites. 

They will be revised in the event additional relevant information is obtained about the affected site(s). 

These documents may be used to assist the National Institute for Occupational Safety and Health 

(NIOSH) in the completion of the individual work required for each dose reconstruction.

In this document the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy facility” as defined in the Energy Employee 

Occupational Illness Compensation Program Act of 2000 [42 U.S.C. Sections 7384l(5) and (12)]. 

EEOICPA defines a DOE facility as “any building, structure, or premise, including the grounds upon 

which such building, structure, or premise is located ... in which operations are, or have been, 

conducted by, or on behalf of, the Department of Energy (except for buildings, structures, premises, 

grounds, or operations ... pertaining to the Naval Nuclear Propulsion Program).” 42 U.S.C. § 

7384l(12). Accordingly, except for the exclusion for the Naval Nuclear Propulsion Program noted 

above, any facility that performs or performed DOE operations of any nature whatsoever is a DOE 

facility encompassed by EEOICPA.

For DOE employees with cancer, the DOE facility definition only determines eligibility for a dose 

reconstruction, which is a prerequisite to a compensation decision (except for members of the Special 

Exposure Cohort). The compensation decision for cancer claimants is based on a section of the 

statute entitled “Exposure in the Performance of Duty.” That provision (42 U.S.C. § 7384n(b)) says 

that an individual with cancer “shall be determined to have sustained that cancer in the performance 

of duty for purposes of the compensation program if, and only if, the cancer ... was at least as likely 

as not related to employment at the facility [where the employee worked], as determined in 

accordance with the [probability of causation] guidelines established under subsection (c) ....” 42 

U.S.C. § 7384n(b). Neither the statute nor the probability of causation guidelines (nor the dose 

reconstruction regulation) define “performance of duty” for DOE employees with a covered cancer or 

restrict the “duty” to nuclear weapons work.

As noted above, the statute includes a definition of a DOE facility that excludes “buildings, structures, 

premises, grounds, or operations covered by Executive Order No. 12344, dated February 1, 1982 (42 

U.S.C. 7158 note), pertaining to the Naval Nuclear Propulsion Program.” 42 U.S.C. § 7384l(12). 

While this definition contains an exclusion with respect to the Naval Nuclear Propulsion Program, the 

section of EEOICPA that deals with the compensation decision for covered employees with cancer 

(i.e., 42 U.S.C. § 7384n(b), entitled “Exposure in the Performance of Duty”) does not contain such an 

exclusion. Therefore, the statute requires NIOSH to include all radiation exposures in its dose 

reconstructions for employees at DOE facilities, including radiation exposures related to the Naval 

Nuclear Propulsion Program. As a result, all internal and external dosimetry results are considered 

valid for use in dose reconstruction. No efforts are made to determine the eligibility of any fraction of 

total measured exposure for inclusion in dose reconstruction.

The Y-12 Plant, now known as the Y-12 National Security Complex, required pre-placement and 

routine physical examinations as part of their occupational health and safety program. These medical 

examinations typically included diagnostic chest X-rays. The doses from these diagnostic X-ray

procedures depended not only on the characteristics of the X-ray machine and the procedure used, 

but also on the frequency of the examination. This section is based primarily on information provided 

by the staff at the present Y-12 Medical X-ray Department (Wiley 2002).
Effective Date: 12/15/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-3 Page 7 of 20

For evaluating Probability of Causation (POC), the doses to be included in calculating the worker’s 

dose are those from diagnostic X-rays that are required by the employer as a condition of 

employment, e.g., X-rays taken for pre-employment, pre-placement, or routine physical examinations. 

These X-rays are referred to in this Technical Basis Document (TBD) as occupational X-rays. Doses 

from diagnostic X-rays taken by either the employer or an off-site health care provider for on-the-job 

or off-the-job injuries or illnesses are not included in the worker’s dose calculation for POC.

3.2 EXAMINATION FREQUENCIES

The frequency of exams differed significantly over the years. The frequency of chest X-rays is shown 

in Table 3-1 for different age groups and for specific groups of workers through the years based on 

information provided by Y-12 (Wiley 2002). 

Table 3-1. Frequency of occupational posterior/anterior chest X-rays at Y-12 (Wiley 2002)a

. 

Period Frequency Comment

1943 to

July 17, 1988

Pre-placement All employees

Annually All employees

At termination All employees

July 18, 1988 to

June 30, 1993

Pre-placement All employees

Time of entry into 

hazardous job

Asbestos and beryllium workers and other jobs with 

potential pulmonary pathogens

Annually Active and previous asbestos and beryllium workers

Every 10 years Employees under 30 years old

Every 5 years Employees aged 30-45 years old

Every 3 years Employees over 45 years old

At termination All employees

July 1, 1993 – 

March 1998

Pre-placement All employees

Time of entry into 

hazardous job

Asbestos and beryllium workers and other jobs with 

potential pulmonary pathogens

Annually Active and previous asbestos and beryllium workers

At termination All employees

March 1998 – 

Present

Pre-placement All employees

Time of entry into 

hazardous job

Asbestos and beryllium workers and other jobs with 

potential pulmonary pathogens

Annually Active asbestos workers

Every 3 years Previous asbestos workers; active and previous beryllium 

workers

At termination All employees

a.) Workers in certain occupations may have received chest X-rays more frequently. This information may be in 

the claimant’s file provided by DOE.

However, occupational X-rays may have occurred more frequently than on the schedule indicated in 

Table 3-1 at least in the early years. Wolf specified more frequent physical examinations (including Xray) for various occupational groups (Wolf 1945). A recommended procedure for post-employment, 

routine medical examinations specified more frequent X-rays for the following occupational groups: 

• Food handlers and cafeteria workers – every 6-12 months

• Alpha (calutron) workers – twice per year

• Liquid phase workers exposed to uranium, phosgene, or carbon tetrachloride – three times per 

year. However, no date was provided on this document. Information on employer-required 

medical X-rays may be available in the claimant’s file.
Effective Date: 10/11/2005 Revision No. 00 PC-2 Document No. ORAUT-TKBS-0014-3 Page 8 of 20

3.3 EQUIPMENT AND TECHNIQUES

The medical practices used at Y-12 are assumed to have followed the adoption of standards of 

radiology practice during the 1930s and 1940s to minimize dose to the patient. However, there is the 

potential for significant dose from occupational medical X-ray examinations, depending on the type of 

equipment, the technique factors, the number of photofluorographic (PFG) examinations typical in the 

early years, and the number of radiographic examinations (Cardarelli et al. 2002). 

According to information provided by the Y-12 Medical X-Ray Department, pre-employment chest Xrays were always taken with a conventional medical diagnostic X-ray machine (Wiley 2002). They 

found no evidence of PFG chest X-rays in the employee medical X-ray folders and all chest X-rays in 

these folders were 14”x17” films. However, in reviewing the medical X-ray folders of workers from the 

1940s, approximately 1400 4”x10” chest X-ray films were found in the medical X-ray folders of 

workers who were employed at Y-12 from 1943 to 1947. Originally these X-rays were thought to be 

copies of conventional X-rays that were taken elsewhere and sent to Y-12 when the person was hired 

there. In fact, these were PFG chest X-rays.

In February 1945, a General Electric (GE) stereoscopic photoroentgen unit is listed as an equipment 

item in the Y-12 Medical Department (Wolf 1945). Reexaminations and other chest films were done 

on conventional 14”x17’ films. On October 12, 1945, the Tennessee Eastman Corporation (TEC) 

Medical Director sent a telegram to the GE X-Ray Corporation, requesting them to set up a 

Photoroentgen Unit 4x10 (Leggo 1945). In June 1946, TEC placed an order with the Oak Ridge 

Hospital for 6000 Eastman-Single Coated 4”x10” X-ray films for the period from August 1, 1946 to July 

31, 1947 (Graham 1946). Thus, it is clear that pre-employment chest X-rays were taken with a PFG 

unit from 1943 to 1947, as evidenced by the 4”x10” films found in the medical records and the 

purchasing records mentioned above. All chest X-rays done since then are conventional 14”x17” Xrays. 

No record has been located to determine what type of diagnostic X-ray machine was in use at Y-12 

from 1948 until the GE-type machine mentioned above that was used in the early 1960s. This date 

may not be correct either. In a meeting with the X-ray technologist who provided the information for 

that report, the technologist said that more recent documentation indicated that the GE-type machine 

was installed in 1969, not in the early 1960s (Beck 2003). Thus, it is not possible at this time to state 

with certainty what X-ray machine was used from 1948 to 1968. From 1969 until January 1982, the 

X-ray machine in use was similar to a GE Model DXD-350. This machine was replaced with a GE 

Model DSX-650II in February 1982 (Wiley 2002).

A description of the X-ray equipment used at Y-12 is included in Table 3-2. The specific technique 

factors for these machines are shown in Table 3-3. Since no technique factors were identified by Y12 for Types I and II equipment, organ doses, based on assumed technique factors, were developed 

on the basis of X-ray techniques contemporary with the time period (1943-1968), with due 

consideration given to claimant favorability. 

Table 3-2. Description of the X-ray equipment used at Y-12. 

Machine Time period Equipment

Type I 1943 to 1947 Photofluorographic unit at Oak Ridge Hospital or Y-12 Clinic

Type II 1948 to 1968 Unknown

Type III 1969 to January 1982 Similar to General Electric Model DXD-350 (exact model unknown)a

Type IV February 1982 to present General Electric DSX 650 II a

a.) From Wiley 2002
Effective Date: 09/09/2004 Revision No. 00 PC-1 Document No. ORAUT-TKBS-0014-3 Page 9 of 20

Table 3-3. Technique factors used for each type of X-ray equipmentb

. 

Machine View

Current

(milliampere [mA])

Voltage

(kilovolts peak [kVp])

Exposure time 

(second [s])

Type I X-rays were done at Oak Ridge Hospital or Y-12. Techniques are unknown. 

No records have been located. 

Type II PAa 200 80 1/20

Type III PA 200 80 1/20 b

Type IV PA 200 110 Photo-timed b

a.) PA indicates a posterior/anterior view, the average PA chest measures 26 cm.

b.) From Wiley 2002

3.4 ORGAN DOSE CALCULATIONS

Most Y-12 employees received occupationally-related diagnostic X-rays annually for many years and 

at a lesser frequency in the later years. The frequency over time (1943-present) for various groups of 

workers is shown in Table 3-1. Only the PFG chests (from 1943-1947) and the posterior/anterior (PA) 

chest views from 1969 to the present are documented.

No actual X-ray output measurements are available. The X-ray technique factors provided may not 

be reliable, especially for the Type II equipment. Thus, default values for entrance kerma will be used 

in the calculation of organ dose conversion factors (DCFs) for use in dose reconstruction. Default 

values have been developed for the three of the most commonly used occupational medical 

diagnostic X-ray procedures: PA, lateral; and PFG chest films (ORAU 2003).. The default values are 

considered to be maxima developed from reviews of patient doses reported in the literature, machine 

characteristics, and knowledge of X-ray procedures used during the time periods indicated. Sufficient 

conservatism was included in the determination of the default values to ensure with near certainty 

(>99% confidence) that the actual exposures from the specified procedures would not exceed the 

default values, thus ensuring claimant favorability. 

In determining the default factors in Table 3-4, it was assumed that minimum filtration was used, along 

with low kilovolt peak (kVp) techniques, slow film speeds with standard development procedures, and 

no additional collimation or use of cones. The default entrance kerma values for the three procedures 

are given in Table 3-4 below.

Table 3-4. Entrance kerma values for Y-12 chest X-rays. 

Period

Entrance kerma (centigray [cGy])

a

Posterior/anterior Photofluorographic

Pre-1970 0.20 3.0

1970-1982 0.10

1982-present 0.05

a. From National Council on Radiation Protection and 

Measurements (NCRP) Report No. 102 (NCRP 1989).

A source-to-image distance (SID) of 72 inches (in) (183 centimeter [cm]) was standard for the time for 

the PA chest, and 42 in (106 cm) for the PFG chests. The X-ray machines used at Y-12 were most 

likely single-phase, and typically no air gap was used between the patient and the film. Before 1982, 

it is assumed that the X-ray equipment was operated at 80 kVp, had at least 1.5 millimeters (mm) 

aluminum (Al) total filtration (see Table 3.1 of National Council on Radiation Protection and 

Measurements [NCRP] [1989]), and that the half value layer (HVL) was approximately 2.5 mm Al 

equivalent [eq.] (see Table B.2 of NCRP [1989]). These were typical machine parameters for chest X-
Effective Date: 04/18/2006 Revision No. 00 PC-3 Document No. ORAUT-TKBS-0014-3 Page 10 of 20

rays performed in this time period. After 1982, the X-ray equipment was operated at 110 kVp and had 

at least 2.5 mm Al total filtration. The HVL was approximately 3.5 mm Al eq. After 1982, the machine 

parameters were the same but the exposures were photo-timed (Wiley 2002). The default values for 

entrance kerma were also used for the PA chest X-rays after 1982 because the exposure time would 

not be known for a photo-timed (automatic) exposure.

The following formula was used to calculate the organ doses in Tables 3C-2, 3, 4, and 5.

Organ dose (rem) = Entrance kerma (cGy) x Organ DCF (mGy/Gy) x 1.0 E-3 (rem-Gy/cGy-mGy)

where, the entrance kerma is in centigray (cGy) and the organ DCF is in milligray (mGy)/gray (Gy). To 

obtain the organ dose in rem, the equation must be multiplied by 1.0 E-03 (rem-Gy/cGy-mGy). 

The appropriate entrance kerma is selected from Table 3-4 and the DCFs are taken from the 

International Commission on Radiological Protection (ICRP) Report No. 34 (ICRP 1982). 

Specific organ doses for the PA chest X-rays and PFG chest films calculated on the basis of the dose 

conversion factors found in ICRP (1982) are given in Tables 3C-2, 3, 4, and 5. Doses for organs not 

listed in ICRP (1982) but specified in the Interactive Radio-Epidemiological Program (IREP) code 

were determined by analogy with anatomical location as indicated in Table 3-5 below. 

It is assumed that the X-ray beam was not collimated for X-rays taken before about 1965. Therefore, 

organs not normally in the primary beam for a PA chest were included in the primary beam by using 

ICRP (1982) organ dose conversion factors (DCFs) for procedures where those organs would 

normally be included in the primary beam or dose data from the literature was used. For example, 

assuming no collimation, the ovaries would be in the primary beam, and DCFs for the abdomen were 

used. Abdomen DCFs were used for ovaries, testes, uterus, and their analogues. The cervical spine 

DCF was used for the thyroid and its analogue.

Table 3-5. Analogues for Interactive RadioEpidemiological Program (IREP) organs not included in 

ICRP (1982). 

Anatomical

location

ICRP 1982

reference organ

IREP organ

analogues

Thorax Lung Thymus

Esophagus

Stomach

Liver/gall bladder

Bone surface

Remainder organs

Abdomen Ovaries Urinary/bladder

Colon/rectum

Head and neck Thyroid Eye/brain

ICRP (1982) provides tables of average absorbed dose in milligray (mGy) in selected organs for 

selected X-ray projections at 1 gray (Gy) entrance kerma (i.e., air kerma without backscatter), for 

selected views (including PA chest), and for selected beam qualities, (i.e., various HVLs). These 

tables provide the basic DCFs for converting air kerma to organ dose. 
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3.5 UNCERTAINTY

Error, defined as deviation from the correct, true or conventionally accepted value of a quantity, and 

uncertainty, defined in terms of the potential range of a stated, measured, assumed or otherwise 

determined value of a quantity, provides an indication of the confidence of the dose estimates. Error 

implies knowledge of what the correct or actual value is, which is, of course, not known. Hence a 

more appropriate term is uncertainty, which is expressed in terms of a confidence level, e.g. 99%. 

This means that the correct or true value, although not actually known, has a 99% probability of falling 

within the range cited. The uncertainty includes both the precision, i.e., how reproducible the 

measurement is, and the accuracy, i.e., how close the measurement or estimate of dose comes to the 

actual or correct value.

In theory a large number of variables can introduce uncertainties or affect the X-ray machine output 

intensity and dose to the patient. In practice only four variables can be reasonably considered to have 

an impact on dose uncertainty. These are variations in (1) applied kVp, (2) beam current, 

(3) exposure time, and (4) distance from the patient to the source of the X-rays (source-to-skin 

distance [SSD]). Other variables, such as the use of screens and grids, reciprocity failure, film speed 

and development, would not affect the beam output intensity.

For a given set of machine settings and parameters, the X-ray output should theoretically be constant 

and unvarying. Although this is not always true in practice, the output is essentially constant unless 

focal spot loading occurs when the power rating of the machine is exceeded. This is unlikely because 

it would be difficult to achieve in practice and would damage the X-ray tube. However, even with the 

use of constant voltage transformers to control line voltages, slight variations may occur in line voltage 

input or other internal voltages, which could alter the kVp of the output beam. For a given kVp setting, 

the variation in kVp falls within ±5% of the machine setting (Seibert et al. 1991). The beam intensity is 

approximately proportional to the 1.7 power of the kilovoltage. This translates to an uncertainty of 

approximately ±8.7% for the output beam intensity in the 76-84 and 105-116 kVp ranges. For 

conservatism, this is rounded up to ±9%.

Similarly, slight variations in tube current are normal. As a tube ages or heats up from usage, the

tube current may change and typically it will drop. Hence, with all other factors remaining constant,

the beam output will be reduced in direct proportion to the change in tube current. Typically, the 

reduction in beam output from current variation is not more than a few per cent under normal 

operating conditions. Large decreases in beam output will be readily detected. This will result in

performing maintenance on the machine to restore the output, or, as a temporary stopgap measure, 

increasing the current or kVp to provide the necessary beam output for proper radiography. For a 

given kVp setting, the beam output is a function of the tube current. A milli-ammeter on the machine 

measures the average tube current. This measurement is subject to uncertainties. In addition, there 

may be minor changes in output as the tube heats up from normal usage, but these variations are 

typically small. Hence the uncertainty in beam output attributable to current variation has been 

estimated at ±5%.

Another parameter that has potential to affect the dose, perhaps significantly, from a diagnostic 

radiograph relates to the exposure time. This can be readily understood by noting that a full-wave 

rectified machine produces 120 pulses per second of X-rays. For an exposure time of 1/20 of a 

second, only six pulses would result. A small error in the timer that resulted in a change of only ±1 

pulse would correspondingly affect the output by ±17%. For an exposure time of 1/30 of a second, the 

change in output corresponding to a deviation of ±1 pulse is ±25%. Early mechanical timers were 

notoriously inaccurate, although timer accuracy improved significantly with the introduction of 
Effective Date: 12/15/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-3 Page 12 of 20

electronic timers. However, once again for conservatism, the uncertainty in the beam output 

attributable to timers will be assumed to have an upper limit of +25%. 

The final factor that is likely to affect patient dose relates to distance from the source of the X-rays, 

which is a determinant of the entrance skin exposure (ESE). For a given individual, the source-to-skin 

distance (SSD) will be determined largely by the thickness of the patient and the accuracy in 

positioning the patient. For a typical patient, this variation in SSD is estimated at no more than a few 

centimeters, with an upper limit of perhaps 7.5 cm. Using the inverse square law, this indicates an 

uncertainty of ±10 % from this source.

Two approaches can be used to determine the combined uncertainty from the above four potential 

sources of uncertainty. The first, and most conservative in that it gives the greatest range, would be 

to assume that the uncertainties are additive. This would give an uncertainty range of up to 

9%+5%+25%+10%=49%. However, a more reasonable approach would be to assume that the 

uncertainties are in fact random, and to compute the statistical root-mean-square (RMS) value. The 

RMS value is simply the square root of the sum of the squares, and computes as ±28.7%. Thus, for 

any individual ESE or derived organ dose, an uncertainty of ±30 % at the 99% confidence level may 

be assumed. For further conservatism, it may be appropriate to assume that errors are all positive, 

and only the + 30% should be used. 
Effective Date: 09/09/2004 Revision No. 00 PC-1 Document No. ORAUT-TKBS-0014-3 Page 13 of 20

REFERENCES

Beck W.L., 2003, “Beck’s Notes on Y-12 Plant Medical X-rays,” Personal Correspondence (e-mail), 

August 13, 2003. 

Cardarelli, J.J., Spitz, H., Rice, C., Buncher, R., Elson, H., and Succop, P., 2002, “Significance of 

Radiation Exposure from Work-Related Chest X-Rays for Epidemiological Studies of Radiation 

Workers,” Amer. J. Ind. Med.,42:490-501. 

Graham, W.H., 1946, “X-Ray Film,” Letter to Dr. F.T. Rogers at Oak Ridge Hospital, June 26, 1946. 

International Commission on Radiological Protection (ICRP), 1982, “Protection of the Worker in 

Diagnostic Radiology,” Annals of the ICRP, ICRP Publication 34, 9(2/3): 1-82.

Leggo, C., 1945, “Telegram to Mr. E.C. Evans,” October 12, 1945.

National Council on Radiation Protection and Measurements (NCRP), 1989, Medical X-Ray, Electron 

Beam and Gamma-Ray Protection up to 50 MeV Equipment Design, Performance and Use), 

NCRP Report No. 102, Bethesda, Maryland.

ORAU (Oak Ridge Associated Universities) 2003, Technical Information Bulletin: Dose 

Reconstruction from Occupationally Related Diagnostic X-ray Procedures, ORAUT-OTIB-0006 

Rev 00, Oak Ridge, Tennessee. November 14, 2003.

Seibert, J. A., G. T. Barnes and R. G. Gould, 1991, Specification, Acceptance Testing, and Quality 

Control of Diagnostic X-ray Imaging Equipment, Medical Physics Monograph No. 20, 

American Institute of Physics, New York.

Webster, E. W., Merrill, O. E., 1957. “Measurements of Gonadal Dose in Radiographic 

Examinations”. New England Journal of Medicine”. 257:811-819.

Wiley, S.W., 2002, Letter to Mr. James Newton, April 10, 2002. 

Wolf, B.S., 1945, “X-ray Department at Y-12, as of 23 February 1945,” Memorandum for the files, 

Army Service Forces, United States Engineer Office, Manhattan District, Oak Ridge, Tennessee, 

February 23, 1945.
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GLOSSARY

Calutron - an electromagnetic apparatus for separating isotopes according to their masses. 

Entrance kerma – see kerma

Entrance skin exposure (ESE) – the exposure at the point where the X-ray beam enters the skin.

Film speed – a measure of the sensitivity of the film to X-rays or light.

Filtration – material in the useful beam which usually absorbs preferentially the less penetrating 

radiation. 

Focal spot – the apparent size of the radiation source region in a source assembly when viewed from 

the central axis of the useful radiation beam. 

Gray (Gy) – the special name for the SI unit of absorbed dose, kerma, and specific energy imparted 

equal to one (1) joule per kilogram (J/kg). (1 Gy = 1 J/kg = 100 rad) 

Grid – a series of lead strips used to improve the quality of radiographic images by removing 

scattered X-rays. 

Half value layer (HVL) – thickness of a specified substance which, when introduced into the path of a 

given beam of radiation, reduces the kerma rate by one-half. (Usually specified in mm Al.)

Interactive RadioEpidemiological Program (IREP) – a computer software program that uses 

information on the dose-response relationship, and specific factors such as a claimant’s radiation 

exposure, gender, age at diagnosis, and age at exposure to calculate the probability of causation for a 

given pattern and level of radiation exposure.

International Commission on Radiological Protection (ICRP) – an independent Registered 

Charity, established to advance for the public benefit the science of radiological protection, in 

particular by providing recommendations and guidance on all aspects of protection against ionising 

radiation.

Inverse square law – the relationship between the exposure rate from a point source of radiation and 

the distance from the source.

Kerma – the sum of the initial kinetic energies of all the charged ionizing particles liberated by 

uncharged ionizing particles per unit mass of a specified material. 

Kiloelectronvolt (keV) – the energy equal to that acquired by a particle with one electron charge in 

passing through a potential difference of 1000 volts. 

Milliammeter – an instrument for measuring electric current in milliamperes. 

National Council on Radiation Protection and Measurements (NCRP) – a nongovernmental, 

public service organization that formulates and disseminates information, guidance and 

recommendations on radiation protection and measurements. 

Organ dose – the dose to a given organ from an X-ray procedure.
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Photofluorography – an obsolete radiographic technique in which the image produced on a 

fluorescent screen by X-rays was photographed. 

Photon - a quantum of electromagnetic radiation. 

Posterior/anterior (P/A) – an X-ray in which the X-ray beam passes from posterior to the anterior 

side of the patient.

Pre-placement X-ray – an X-ray, usually a chest X-ray, taken before a worker is hired or assigned to 

a specific job.

Probability of causation (POC) – the probability or likelihood that a cancer was caused by radiation 

exposure incurred by a covered employee in the performance of duty. 

Pulmonary - relating to, functioning like, or associated with the lungs. 

Root-mean-square - the square root of the arithmetic mean of the squares of a set of numbers. 

Screens – a fluorescent material used in diagnostic radiology that absorbs the X-rays and converts it 

into light that exposes the X-ray film.

Source-to-image distance (SID) – the distance measured along the central ray from the center of 

the front of the surface of the source (focal spot) to the surface of the image detector. 

Source-to-skin distance (SSD) – the distance measured along the central ray from the center of the 

front of the surface of the source (focal spot) to the surface of the irradiated object or the patient. 

Technique factors – the variables, i.e., the peak voltage (kVp), current (mA), and time (s), that are 

used for taking an X-ray.

Termination X-ray – an X-ray, usually a chest X-ray that is taken when the employee is separated 

from the company.

Tube current – the current flowing through the filament or cathode in an X-ray tube.

Variable – a quantity that may assume any one of a set of values.

X-ray - electromagnetic radiation of the same nature as visible radiation but having an extremely short 

wavelength of less than 10-8 m; a photograph obtained by use of X rays.

X-ray tube – an evacuated electronic tube in which X-rays are generated when electrons are 

accelerated by an applied voltage and strike an anode or target. 
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ATTACHMENT 3C 

OCCUPATIONAL MEDICAL DOSE

TABLE OF CONTENTS

Section

3C.1 Y-12 Medical X-ray Program..................................................................................................

Page

17

3C.2 Organ Doses from Medical X-rays ......................................................................................... 17

3C.3 Dose Reconstructor Instructions ............................................................................................ 17

3C.3.1 Assignment of Organ Doses from X-ray Procedures: Maximizing 

Approach for Dose Reconstructions .............................................................................. 18

3C.3.2 Assignment of Organ Doses from X-ray Procedures: Best Estimate 

Approach for Dose Reconstructions .............................................................................. 18

LIST OF TABLES

Table

3C-1 Frequency of occupational chest x-rays at Y-12.....................................................................

Page

17

3C-2 Organ doses (rem) for a beam quality (HVL) of 2.5 mm Al and 80 kVp 

(1943-1947) ...........................................................................................................................19

3C-3 Organ doses (rem) for a beam quality (HVL) of 2.5 mm Al and 80 kVp 

(1948-1968) assuming no collimation..................................................................................... 19

3C-4 Organ doses (rem)a for a beam quality (HVL) of 2.5 mm Al and 80 kVp 

(1969-January 1982).............................................................................................................. 20

3C-5 Organ doses (rem)a for a beam quality (HVL) of 3.5 mm Al and 110 kVp 

(January 1982-present).......................................................................................................... 20
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3C.1 Y-12 MEDICAL X-RAY PROGRAM

Y-12 conducted pre-placement and annual physical examinations as part of their occupational health 

program. These examinations typically included a chest X-ray. In general, the frequency of the 

examinations over the years and by age of the worker is shown in Table 3C-1 (Wiley 2002). For 

some workers, and occupations, chest X-rays could be more frequent. For example, food handlers 

and cafeteria workers were examined every 6-12 months; alpha (calutron) workers were examined 

twice per year; and liquid phase workers exposed to uranium, phosgene or carbon tetrachloride 

underwent three examinations per year.

Table 3C-1. Frequency of occupational posterior/anterior chest X-rays at Y-12 (Wiley 2002).a

 

Period Frequency Comment

1943 –

Present

Pre-placement All employees

At termination All employees

1943 –

July 18,1988

Annually All employees

July 18, 1988 – 

Present

Time of entry into 

hazardous job

Asbestos and beryllium workers and other jobs with potential 

pulmonary pathogens

July 18, 1988 –

March 1998

Annually Active and previous asbestos and beryllium workers

July 18, 1988 – 

June 30, 1993

Every 10 years Employees under 30 years old

Every 5 years Employees aged 30-45 years old

Every 3 years Employees over 45 years old

March 1998 – 

Present

Annually Active asbestos workers

Every 3 years Previous asbestos workers; active and previous beryllium workers

a.) Workers in certain occupations may have received chest X-rays more frequently. This information may be in 

the claimant’s file provided by DOE.

3C.2 ORGAN DOSES FROM MEDICAL X-RAYS 

X-ray organ doses for occupational X-rays at Y-12 are estimated for all years from 1943 to present. 

The schedule for these exams for all Y-12 employees over this time period is shown in Table 3C-1. 

The organ dose estimates are provided in Tables 3C-2, 3, and 4. The X-ray organ dose estimates 

were made for Type I equipment (used from 1943 to 1947), Type II equipment (used from 1948 to 

1968), Type III equipment (used from 1969 to January 1982), and Type IV equipment (used from 

February 1982 to present) (Wiley 2002). 

For organs outside the chest cavity, other ICRP (1982) organ dose conversion factors (DCFs) besides 

PA chest were used to ensure that the organ doses reflected their presence in the primary beam. For 

example, the dose to the ovaries for Type I equipment assumes they were in the primary beam, so 

the air kerma at the skin was multiplied by the DCF for ovaries in the abdomen.

3C.3 DOSE RECONSTRUCTOR INSTRUCTIONS

The information given below summarizes instructions given to the dose reconstructors in determining 

organ doses from occupational medical X-ray procedures. For the purpose of evaluating probability of 

causation (POC), X-ray doses are always considered acute, and are considered to be photons with 

energies in the range from 30 to 250 kiloelectronvolts (keV).
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3C.3.1

Organ doses from X-ray procedures have been calculated and are presented in Tables 3C-2, 3, 4, 

and 5. The organ doses assigned for each X-ray procedure are the highest doses to any organ in the 

relevant group as listed in Tables 3C-2 to 5,. One annual X-ray procedure for each full or partial year 

of employment is assumed. However, if the dose reconstructor determines that more frequent 

procedures occurred or may have occurred, the annual organ doses can be raised accordingly. As 

mentioned above in 3C.1, the TEC specified more frequent examinations for certain occupations. The 

dose reconstructor should assume that food handlers and cafeteria workers, and alpha calutron 

workers received two (2) X-rays per year; liquid phase workers exposed to uranium, phosgene or 

carbon tetrachloride received three examinations per year. Since this was a TEC guideline, the 

higher frequency of X-ray examinations should be applied only during TEC’s tenure at Y-12 (1943 to 

1947).

Assignment of Organ Doses from X-ray Procedures: Maximizing Approach for Dose 

Reconstructions

The X-ray doses presented above are treated as a point estimate (constant) for the purpose of 

calculating probability of causation. 

3C.3.2

For the dose calculation, a normal distribution is applied with a standard deviation of 30%. The value 

of the standard deviation is equal to the mean value times 30%. Thus, the dose reconstructor should 

multiply the organ doses listed in Tables C-2, 3, 4, and 5 by 1.3. The dose reconstructor may use a 

frequency other than annual if the actual frequency is known and apply the guidance in 3C.3.1 above. 

Assignment of Organ Doses from X-ray Procedures: Best Estimate Approach for 

Dose Reconstructions

1 
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Table 3C-2. Organ doses (rem)a for a beam 

quality (HVL) of 2.5 mm Al and 80 kVp (Type I 

machine; 1943-1947). 

Organ

Organ dose from 

photofluorographic 

chest X-ray (rem)

Entrance air kerma 3.00E+00b

Thyroid c 5.22E-01

Eye/brain 9.60E-02

Ovaries e 2.5 E-02 

Liver/gall bladder 1.35E+00

Urinary bladder e 2.5 E-02 

Colon/rectum e 2.5 E-02 

Testes e 5.0 E-03 

Lungs (male) 1.26E+00

Lungs (female) 1.35E+00

Thymus 1.35E+00

Esophagus 1.35E+00

Stomach 1.35E+00

Bone surface 1.35E+00

Remainder 1.35E+00

Breast 1.47E-01

Uterus e 2.5 E-02 

Bone marrow (male) 2.76E-01

Bone marrow (female) 2.58E-01

Skin d 4.05E+00

a. For organs listed in ICRP 34 (1982) and proximal 

organs for input to IREP.

b. ORAU (2003). 

c. The DCF for the AP cervical spine was used, 

corrected by a 20% depth dose factor (NCRP (1989), 

Table B-8). 

d. Skin dose is entrance skin kerma, multiplied by a 

backscatter factor of 1.35 from NCRP 102, Table B8.

e. Modified from Webster. 

Table 3C-3. Organ doses (rem) a for a beam 

quality (HVL) of 2.5 mm Al and 80 kVp (Type II 

machine; 1948-1968) assuming no collimation. 

Organ

Organ dose from 

posterior/anterior 

chest X-ray (rem)

Entrance air kerma 2.00E-01b

Thyroid c 3.48E-02

Eye/brain 6.40E-03

Ovaries e 2.50E-02

Liver/gall bladder 9.02E-02

Urinary bladder e 2.50E-02

Colon/rectum e 2.50E-02

Testes e 5.00E-03

Lungs (male) 8.38E-02

Lungs (female) 9.02E-02

Thymus 9.02E-02

Esophagus 9.02E-02

Stomach 9.02E-02

Bone surface 9.02E-02

Remainder 9.02E-02

Breast 9.80E-03

Uterus e 2.50E-02

Bone marrow (male) 1.84E-02

Bone marrow (female) 1.72E-02

Skin d 2.70E-01

a. For organs listed in ICRP (1982) and proximal 

organs for input to IREP.

b. ORAU (2003). 

c. The DCF for the AP cervical spine was used, 

corrected by a 20% depth dose factor (NCRP (1989), 

Table B-8). 

d. Skin dose is entrance skin kerma, multiplied by a 

backscatter factor of 1.35 from NCRP (1989), Table 

B-8.

e. Modified from Webster.
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Table 3C-4. Organ doses (rem)a for a beam 

quality (HVL) of 2.5 mm Al and 80 kVp (1969-

January 1982). 

Organ

Organ dose from 

Posterior/anterior 

chest X-ray (rem)

Entrance air kerma 1.00E-01b

Thyroid 3.20E-03

Eye/brain 3.20E-03

Ovaries 1.00E-04

Liver/gall bladder 4.51E-02

Urinary bladder 1.00E-04

Colon/rectum 1.00E-04

Testes 1.00E-06

Lungs (male) 4.19E-02

Lungs (female) 4.51E-02

Thymus 4.51E-02

Esophagus 4.51E-02

Stomach 4.51E-02

Bone surface 4.51E-02

Remainder 4.51E-02

Breast 4.90E-03

Uterus 1.30E-04

Bone marrow (male) 9.20E-03

Bone marrow (female) 8.60E-03

Skin c 1.35E-01

a. For organs listed in ICRP (1982) and proximal 

organs for input to IREP.

b. ORAU (2003). 

c. Skin dose is entrance skin kerma, multiplied by a 

backscatter factor of 1.35 from NCRP (1989), Table 

B-8.

Table 3C-5. Organ doses (rem)a for a beam 

quality (HVL) of 3.5 mm Al and 110 kVp 

(January 1982-present). 

Organ

Organ dose from 

posterior/anterior 

chest X-ray (rem)

Entrance air kerma 5.00E-02b

Thyroid 3.10E-03

Eye/brain 3.10E-03

Ovaries 1.60E-04

Liver/gall bladder 3.05E-02

Urinary bladder 1.60E-04

Colon/rectum 1.60E-04

Testes 5.00E-07

Lungs (male) 2.83E-02

Lungs (female) 3.05E-02

Thymus 3.05E-02

Esophagus 3.05E-02

Stomach 3.05E-02

Bone surface 3.05E-02

Remainder 3.05E-02

Breast 4.55E-03

Uterus 1.50E-04

Bone marrow (male) 7.30E-03

Bone marrow (female) 7.05E-03

Skin c 7.00E-02

a. For organs listed in ICRP (1982) and proximal 

organs for input to IREP. 

b. ORAU (2003). 

c. Skin dose is entrance skin kerma, multiplied by a 

backscatter factor of 1.4 from NCRP (1989), Table B8.